Computational rationality and voluntary provision of public goods: an agent-based simulation model

The issue of the cooperation among private agents in realising collective goods has always raised problems concerning the basic nature of individual behaviour as well as the more traditional economic problems. The Computational Economics literature on public goods provision can be useful to study the possibility of cooperation under alternative sets of assumptions concerning the nature of individual rationality and the kind of interactions between individuals. In this work I will use an agent-based simulation model to study the evolution of cooperation among private agents taking part in a collective project: a high number of agents, characterised by computational rationality, defined as the capacity to calculate and evaluate their own immediate payoffs perfectly and without errors, interact to producing a public good. The results show that when the agents’ behaviour is not influenced either by expectations of others’ behaviour or by social and relational characteristics, they opt to contribute to the public good to an almost socially optimal extent, even where there is no big difference between the rates of return on the private and the public investment.Computational Economics; Agent-based models; Social Dilemmas; Collective Action; Public Goods

Social capital, local institutions, and cooperation between firms

There are many different reasons behind cooperation between firms and many possible interpretations are assumed to be based on an assessment of endogenous benefits of collective action directly generated by taking part in a joint project. This paper attempts at verifying the interpretative capacity of models analysing the cooperation between firms using not only technological or organisational factors and rivalry between firms, but also some proxy variables of social capital, of experience accumulation in collective action and of institutional capacity for initiative. The specific aim of our work is hence that of providing an interpretation of Italian inter-province differentials in the propensity of inter-firm cooperation.35

Non-linear conductivity and quantum interference in disordered metals

We report on a novel non-linear electric field effect in the conductivity of disordered conductors. We find that an electric field gives rise to dephasing in the particle-hole channel, which depresses the interference effects due to disorder and interaction and leads to a non-linear conductivity. This non-linear effect introduces a field dependent temperature scale $T_E$ and provides a microscopic mechanism for electric field scaling at the metal-insulator transition. We also study the magnetic field dependence of the non-linear conductivity and suggest possible ways to experimentally verify our predictions. These effects offer a new probe to test the role of quantum interference at the metal-insulator transition in disordered conductors.Comment: 5 pages, 3 figure

Theory of the spin galvanic effect at oxide interfaces

The spin galvanic effect (SGE) describes the conversion of a non-equilibrium spin polarization into a transverse charge current. Recent experiments have demonstrated a large conversion efficiency for the two-dimensional electron gas formed at the interface between two insulating oxides, LaAlO$_3$ and SrTiO$_3$. Here we analyze the SGE for oxide interfaces within a three-band model for the Ti t$_{2g}$ orbitals which displays an interesting variety of effective spin-orbit couplings in the individual bands that contribute differently to the spin-charge conversion. Our analytical approach is supplemented by a numerical treatment where we also investigate the influence of disorder and temperature, which turns out to be crucial to provide an appropriate description of the experimental data.Comment: 5 pages, 3 figure

Current-induced spin polarization and the spin Hall effect: a quasiclassical approach

The quasiclassical Green function formalism is used to describe charge and spin dynamics in the presence of spin-orbit coupling. We review the results obtained for the spin Hall effect on restricted geometries. The role of boundaries is discussed in the framework of spin diffusion equations.Comment: 10 pages, 5 figures, Submitted to Solid State Communications Special Issue on "Fundamental Phenomena in Low Dimensional Electron Systems". Special Issue Editors: Marco Polini, Michele Governale, Hermann Grabert, Vittorio Pellegrini, and Mario Tos

High luminosity interaction region design for collisions with detector solenoid

An innovatory interaction region has been recently conceived and realized on the Frascati DA{\Phi}NE lepton collider. The concept of tight focusing and small crossing angle adopted until now to achieve high luminosity in multibunch collisions has evolved towards enhanced beam focusing at the interaction point with large horizontal crossing angle, thanks to a new compensation mechanism for the beam-beam resonances. The novel configuration has been tested with a small detector without solenoidal field yielding a remarkable improvement in terms of peak as well as integrated luminosity. The high luminosity interaction region has now been modified to host a large detector with a strong solenoidal field which significantly perturbs the beam optics introducing new design challenges in terms of interaction region optics design, beam transverse coupling control and beam stay clear requirementsComment: 3 pages, 4 figures, presented to the IPAC10 conferenc

Tuning Knobs for the NLC Final Focus

Compensation of optics errors at the Interaction Point (IP) is essential for maintaining maximum luminosity at the NLC. Several correction systems (knobs) using the Final Focus sextupoles have been designed to provide orthogonal compensation of linear and the second order optics aberrations at IP. Tuning effects of these knobs on the 250 GeV beam were verified using tracking simulations.Comment: 4 pages, 3 figure